Layout pattern of magnetoresistive random access memory

ABSTRACT

A layout pattern of a magnetoresistive random access memory (MRAM) includes a substrate having a first cell region, a second cell region, a third cell region, and a fourth cell region and a diffusion region on the substrate extending through the first cell region, the second cell region, the third cell region, and the fourth cell region. Preferably, the diffusion region includes a H-shape according to a top view.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a layout pattern for magnetoresistive randomaccess memory (MRAM).

2. Description of the Prior Art

Magnetoresistance (MR) effect has been known as a kind of effect causedby altering the resistance of a material through variation of outsidemagnetic field. The physical definition of such effect is defined as avariation in resistance obtained by dividing a difference in resistanceunder no magnetic interference by the original resistance. Currently, MReffect has been successfully utilized in production of hard disksthereby having important commercial values. Moreover, thecharacterization of utilizing GMR materials to generate differentresistance under different magnetized states could also be used tofabricate MRAM devices, which typically has the advantage of keepingstored data even when the device is not connected to an electricalsource.

The aforementioned MR effect has also been used in magnetic field sensorareas including but not limited to for example electronic compasscomponents used in global positioning system (GPS) of cellular phonesfor providing information regarding moving location to users. Currently,various magnetic field sensor technologies such as anisotropicmagnetoresistance (AMR) sensors, GMR sensors, magnetic tunnelingjunction (MTJ) sensors have been widely developed in the market.Nevertheless, most of these products still pose numerous shortcomingssuch as high chip area, high cost, high power consumption, limitedsensibility, and easily affected by temperature variation and how tocome up with an improved device to resolve these issues has become animportant task in this field.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a layout pattern ofa magnetoresistive random access memory (MRAM) includes a substratehaving a first cell region, a second cell region, a third cell region,and a fourth cell region and a diffusion region on the substrateextending through the first cell region, the second cell region, thethird cell region, and the fourth cell region. Preferably, the diffusionregion includes a H-shape according to a top view.

According to another aspect of the present invention, a layout patternof a magnetoresistive random access memory (MRAM) includes a substratehaving a first cell region and a second cell region and a diffusionregion on the substrate extending through the first cell region and thesecond cell region. Preferably, the diffusion region includes a firstH-shape and a second H-shape according to a top view.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrate a layout pattern of a MRAM device according to anembodiment of the present invention.

FIGS. 6-10 illustrate a layout pattern of a MRAM device according to anembodiment of the present invention.

DETAILED DESCRIPTION

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, manufacturers may refer to a component by different names.This document does not intend to distinguish between components thatdiffer in name but not function. In the following discussion and in theclaims, the terms “including” and “comprising” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . ” The terms “connect”, “couple” and “couples” areintended to mean either an indirect or a direct electrical connection.Thus, if a first device couples to a second device, that connection maybe through a direct electrical connection, or through an indirectelectrical connection via other devices and connections.

Referring to FIGS. 1-5, FIGS. 1-5 illustrate a layout pattern of a MRAMdevice with elements in different levels according to an embodiment ofthe present invention. As shown in FIG. 1, a substrate 12 made ofsemiconductor material is provided, in which the substrate 12 could beselected from the group consisting of silicon (Si), germanium (Ge),Si—Ge compounds, silicon carbide (SiC), and gallium arsenide (GaAs).Next, a first cell region 14, a second cell region 16, a third cellregion 18, and a fourth cell region 20 are defined on the substrate 12,in which each of the cell region or memory cell region preferablyincludes two sets of transistors and a MTJ for constituting a 2T1MTJcell structure.

The substrate 12 preferably includes a diffusion region 22 extendingthrough the first cell region 14, the second cell region 16, the thirdcell region 18, and the fourth cell region 20, in which the diffusionregion 22 includes a H-shape according to a top view perspective.Specifically, the diffusion region 22 further includes a first portion24 extending from the first cell region 14 to the third cell region 18along a first direction (such as Y-direction), a second portion 26extending from the second cell region 16 to the fourth cell region 20along the first direction, a third portion 28 extending from the firstcell region 14 to the second cell region 16 along a second direction(X-direction) for connecting the first portion 24 and the second portion26, a fourth portion 30 extending from the third cell region 18 to thefourth cell region 20 along the second direction for connecting thefirst portion 24 and the second portion 26, and a fifth portion 32extending between the third portion 28 and the fourth portion 30 alongthe second direction for connecting the first portion 24 and the secondportion 26.

Viewing from an overall perspective the third portion 28, the fourthportion 30, and the fifth portion 32 are all disposed extending alongthe X-direction and parallel to each other, and the fifth portion 32 isdisposed between the third portion 28 and the fourth portion 30 whileoverlapping the first cell region 14, the second cell region 16, thethird cell region 18, and the fourth cell region 20.

A plurality of gate patterns or word lines (WLs) including a first gatepattern 34, a second gate pattern 36, a third gate pattern 38, and afourth pattern 40 are disposed on the diffusion region 22, in which thefirst gate pattern 34 is extending from the first cell region 14 to thesecond cell region 16 along the second direction, the second gatepattern 36 is extending from the first cell region 14 to the second cellregion 16 along the second direction, the third gate pattern 38 isextending from the third cell region 18 to the fourth cell region 20along the second direction, and the fourth gate pattern 40 is extendingfrom the third cell region 18 to the fourth cell region 20 along thesecond direction.

The MRAM device further includes a first source region S₁ disposed onthe third portion 28, a second source region S₂ disposed on the fourthportion 30, a third source region S₃ disposed on the fifth portion 32, afirst drain region D₁ disposed on the first cell region 14 between thefirst gate pattern 34 and the second gate pattern 36, a second drainregion D₂ disposed on the second cell region 16 between the first gatepattern 34 and the second gate pattern 36, a third drain region D₃disposed on the third cell region 18 between the third gate pattern 38and the fourth gate pattern 40, and a fourth drain region D₄ disposed onthe fourth cell region 20 between the third gate pattern 38 and thefourth gate pattern 40. It should be noted that a contact plug (notshown) having rectangular profile is disposed on each of the firstsource region S₁, second source region S₂, third source region S₃, firstdrain region D₁, second drain region D₂, third drain region D₃, andfourth drain region D₄ for connecting the source and drain regions tothe first level metal patterns formed afterwards while the source anddrain regions are essentially disposed adjacent to two sides of the gatepatterns and not limited in the rectangular blocks.

As shown in FIG. 2, the MRAM device further includes a plurality offirst level metal patterns M1 disposed on the first cell region 14, thesecond cell region 16, the third cell region 18, and the fourth cellregion 20 while overlapping each of the gate patterns, in which thefirst level metal patterns include a first metal pattern 42 extendingalong the first direction such as Y-direction overlapping and connectingthe first source region S₁, the second source region S₂, and the thirdsource region S₃, a second metal pattern 44 extending along the firstdirection overlapping and connecting the first drain region D₁, a thirdmetal pattern 46 extending along the first direction overlapping andconnecting the second drain region D₂, a fourth metal pattern 48extending along the first direction overlapping and connecting the thirddrain region D₃, and a fifth metal pattern 50 extending along the firstdirection overlapping and connecting the fourth drain region D₄.

Viewing from a top view perspective, each of the first metal pattern 42,second metal pattern 44, third metal pattern 46, fourth metal pattern48, and fifth metal pattern 50 include a rectangular shape extendingalong the Y-direction and overlapping the source regions and drainregions in the cell regions. It should be noted that the first metalpattern 42 from the first level metal patterns is coupled to or directlyconnecting to a source line (SL) so that signals could be transmitted onthe same level.

MRAM device also includes a plurality of first level via patterns (alsoreferred to as V1) disposed on the first level metal patterns on thefirst cell region 14, second cell region 16, third cell region 18, andfourth cell region 20, in which the first level via patterns include avia pattern 52 disposed on the second metal pattern 44, a via pattern 54disposed on the third metal pattern 46, a via pattern 56 disposed on thefourth metal pattern 48, and a via pattern 58 disposed on the fifthmetal pattern 50.

Next, as shown in FIG. 3, the MRAM device further includes a pluralityof second level metal patterns M2 disposed on and overlapping each ofthe first level metal patterns and first level via patterns on the firstcell region 14, second cell region 16, third cell region 18, and fourthcell region 20, in which the second level metal patterns includes ametal pattern 62 overlapping the second metal pattern 44 on the firstcell region 14, a metal pattern 64 overlapping the third metal pattern46 on the second cell region 16, a metal pattern 66 overlapping thefourth metal pattern 48 on the third cell region 18, and a metal pattern68 overlapping the fifth metal pattern 50 on the fourth cell region 20.Viewing from a top view perspective, each of the metal patterns from thesecond level metal patterns include a substantially square shapeoverlapping the drain regions disposed on each of the cell regions.

Next, as shown in FIG. 4, the MRAM device includes a plurality of MTJsdisposed on the second level metal patterns and coupled to the lowerlevel second level metal interconnections and even lower level drainregions, in which the MTJs include a first MTJ 72 disposed on the metalpattern 62 on the first cell region 14 and connected to the first drainregion D₁, a second MTJ 74 disposed on the metal pattern 64 on thesecond cell region 16 and connected to the second drain region D₂, athird MTJ 76 disposed on the metal pattern 66 on the third cell region18 and connected to the third drain region D₃, and a fourth MTJ 78disposed on the metal pattern 68 on the fourth cell region 20 andconnected to the fourth drain region D₄. Since the MTJs are disposed onthe second level metal patterns, the MTJs could be understood as thirdlevel metal patterns M3.

In this embodiment, each of the MTJs preferably includes a bottomelectrode, a pinned layer, a barrier layer, a free layer, and a topelectrode disposed on the second level metal patterns. Preferably, thebottom electrode layer and the top electrode layer are made ofconductive material including but not limited to for example Ta, Pt, Cu,Au, Al, or combination thereof. The pinned layer could be made offerromagnetic material including but not limited to for example iron,cobalt, nickel, or alloys thereof such as cobalt-iron-boron (CoFeB) orcobalt-iron (CoFe). Moreover, the pinned layer could also be made ofantiferromagnetic (AFM) material including but not limited to forexample ferromanganese (FeMn), platinum manganese (PtMn), iridiummanganese (IrMn), nickel oxide (NiO), or combination thereof, in whichthe pinned layer is formed to fix or limit the direction of magneticmoment of adjacent layers. The barrier layer could be made of insulatingmaterial including but not limited to for example oxides such asaluminum oxide (AlO_(x)) or magnesium oxide (MgO). The free layer couldbe made of ferromagnetic material including but not limited to forexample iron, cobalt, nickel, or alloys thereof such ascobalt-iron-boron (CoFeB), in which the magnetized direction of the freelayer could be altered freely depending on the influence of outsidemagnetic field.

Overall, each of the cell regions includes a 2T1MTJ cell structure thatpreferably includes two transistors accompanying a single MTJ. Forinstance, a first source region S₁, a first gate pattern 34, a firstdrain region D₁, a second gate pattern 36, a third source region D₃, anda first MTJ 72 disposed on the first cell region 14 preferablyconstitute a 2T1MTJ cell structure in the first cell region 14.

Next, as shown in FIG. 5, the MRAM device includes a plurality of fourthlevel metal patterns M4 disposed on the first cell region 14, secondcell region 16, third cell region 18, and fourth cell region 20 tooverlap the MTJs, in which the fourth level metal patterns include ametal pattern 82 extending from the first cell region 14 to the thirdcell region 18 along the first direction such as Y-direction to overlapthe first MTJ 72 and the third MTJ 76 and a metal pattern 84 extendingfrom the second cell region 16 to the fourth cell region 20 along thesame first direction to overlap the second MTJ 74 and the fourth MTJ 78.

Viewing from a top view perspective, each of the metal patterns from thefourth level metal patterns include rectangular shape extending alongthe Y-direction and overlapping the drain region and MTJ disposed ineach cell region. It should also be noted that each of the metalpatterns 82, 84 from the fourth level metal patterns are also coupled toor directly connected to a bit line (BL) for passing the signals.

Referring to FIGS. 6-10, FIGS. 6-10 illustrate a layout pattern of aMRAM device according to an embodiment of the present invention. Forsimplicity purpose, elements from the aforementioned embodiments arelabeled with same numberings. As shown in FIG. 6, a substrate 112 madeof semiconductor material is provided, in which the substrate 112 couldbe selected from the group consisting of silicon (Si), germanium (Ge),Si—Ge compounds, silicon carbide (SiC), and gallium arsenide (GaAs).Next, a first cell region 114 and a second cell region 116 are definedon the substrate 112, in which each of the cell region or memory cellregion preferably includes three sets of transistors and two MTJs forconstituting a 3T2MTJ cell structure.

The substrate 112 preferably includes a diffusion region 122 extendingthrough the first cell region 114 and the second cell region 116, inwhich the diffusion region 122 includes a first H-shape and a secondH-shape according to a top view perspective. Specifically, the diffusionregion 122 further includes a first portion 124 extending in the firstcell region 114 along a first direction (such as Y-direction), a secondportion 126 extending in the second cell region 116 along the firstdirection, a third portion 128 extending from the first cell region 114to the second cell region 116 along a second direction (X-direction) forconnecting the first portion 124 and the second portion 126, and afourth portion 130 extending from the first cell region 114 to thesecond cell region 116 along the second direction for connecting thefirst portion 124 and the second portion 126.

It should be noted that viewing from a top view perspective, the thirdportion 128 and the fourth portion 130 preferably overlaps theboundaries of the first cell region 114 and second cell region 116 andpart of the first portion 124, second portion 126, third portion 128,and fourth portion 130 exceed the boundaries of the first cell region114 and second cell region 116. Nevertheless, according to otherembodiment of the present invention it would also be desirable tocontain all the outer boundary of the first portion 124, second portion126, third portion 128, and fourth portion 130 within the first cellregion 114 and second cell region 116 so that all the four portions ofthe diffusion region 122 do not cross over the boundaries of the twocell regions, which is also within the scope of the present invention.

The MRAM device further includes a plurality of gate patterns such as afirst gate pattern 134, a second gate pattern 136, and a third gatepattern 138 disposed on the diffusion region 22, in which the first gatepattern 134 is extending from the first cell region 114 to the secondcell region 116 along the second direction, the second gate pattern 136is extending from the first cell region 114 to the second cell region116 along the second direction, and the third gate pattern 138 isextending from the first cell region 114 to the second cell region 116along the second direction.

The MRAM device further includes a first source region S₁ disposed onthe third portion 128, a second source region S₂ disposed on the fourthportion 130, a first drain region D₁ disposed on the first cell region114 between the first gate pattern 134 and the second gate pattern 136,a second drain region D₂ disposed on the second cell region 116 betweenthe first gate pattern 134 and the second gate pattern 136, a thirddrain region D₃ disposed on the first cell region 114 between the secondgate pattern 136 and the third gate pattern 138, and a fourth drainregion D₄ disposed on the second cell region 116 between the second gatepattern 136 and the third gate pattern 138. Similar to theaforementioned embodiment, a contact plug (not labeled) havingrectangular shape is disposed on each of the first source region S₁,second source region S₂, first drain region D₁, second drain region D₂,third drain region D₃, and fourth drain region D₄ for connecting thesource and drain regions to the first level metal patterns formedafterwards while the source and drain regions are essentially disposedadjacent to two sides of the gate patterns and not limited in therectangular blocks.

As shown in FIG. 7, the MRAM device further includes a plurality offirst level metal patterns M1 disposed on the first cell region 114 andthe second cell region 116 while overlapping each of the gate patterns,in which the first level metal patterns include a first metal pattern142 extending along the first direction such as Y-direction overlappingand connecting the first source region S₁ and the second source regionS₂, a second metal pattern 144 extending along the first directionoverlapping and connecting the first drain region D₁, a third metalpattern 146 extending along the first direction overlapping andconnecting the second drain region D₂, a fourth metal pattern 148extending along the first direction overlapping and connecting the thirddrain region D₃, and a fifth metal pattern 150 extending along the firstdirection overlapping and connecting the fourth drain region D₄.

Viewing from a top view perspective, each of the first metal pattern142, second metal pattern 144, third metal pattern 146, fourth metalpattern 148, and fifth metal pattern 150 include a rectangular shapeextending along the Y-direction and overlapping the source regions anddrain regions in the cell regions. Similar to the aforementionedembodiment, the first metal pattern 142 from the first level metalpatterns is coupled to or directly connecting to a source line (SL) sothat signals could be transmitted on the same level.

MRAM device also includes a plurality of first level via patterns (alsoreferred to as V1) disposed on the first level metal patterns on thefirst cell region 114 and second cell region 116, in which the firstlevel via patterns include a via pattern 152 disposed on the secondmetal pattern 144, a via pattern 154 disposed on the third metal pattern146, a via pattern 156 disposed on the fourth metal pattern 148, and avia pattern 158 disposed on the fifth metal pattern 150.

Next, as shown in FIG. 8, the MRAM device further includes a pluralityof second level metal patterns M2 disposed on and overlapping each ofthe first level metal patterns and first level via patterns on the firstcell region 114 and second cell region 116, in which the second levelmetal patterns includes a metal pattern 162 overlapping the second metalpattern 144 on the first cell region 114, a metal pattern 164overlapping the third metal pattern 146 on the second cell region 116, ametal pattern 166 overlapping the fourth metal pattern 148 on the firstcell region 114, and a metal pattern 168 overlapping the fifth metalpattern 150 on the second cell region 116. Viewing from a top viewperspective, each of the metal patterns from the second level metalpatterns include a substantially square shape overlapping the drainregions disposed on each of the cell regions.

Next, as shown in FIG. 9, the MRAM device includes a plurality of MTJsdisposed on the second level metal patterns and coupled to the lowerlevel second level metal patterns and even lower level drain regions, inwhich the MTJs include a first MTJ 172 disposed on the metal pattern 162on the first cell region 114 and connected to the first drain region D₁,a second MTJ 174 disposed on the metal pattern 164 on the second cellregion 116 and connected to the second drain region D₂, a third MTJ 176disposed on the metal pattern 166 on the first cell region 114 andconnected to the third drain region D₃, and a fourth MTJ 178 disposed onthe metal pattern 168 on the second cell region 116 and connected to thefourth drain region D₄. Similar to the aforementioned embodiment, eachof the MTJs preferably includes a bottom electrode, a pinned layer, abarrier layer, a free layer, and a top electrode disposed on the secondlevel metal patterns.

Overall, each of the cell regions includes a 3T2MTJ cell structure thatpreferably includes three transistors accompanying two MTJs. Forinstance, a first source region S₁, a first gate pattern 134, a firstdrain region D₁, a second gate pattern 136, a third drain region D₃, athird gate pattern 138, a second source region S₂, a first MTJ 172, anda third MTJ 176 disposed on the first cell region 114 preferablyconstitute a 3T2MTJ cell structure in the first cell region 114.

Next, as shown in FIG. 10, the MRAM device includes a plurality offourth level metal patterns M4 disposed on the first cell region 114 andsecond cell region 116 to overlap the MTJs, in which the fourth levelmetal patterns include metal patterns 182, 184 extending along the firstdirection such as Y-direction in the first cell region 114 to overlapthe first MTJ 172 and the third MTJ 176 and metal patterns 186, 188extending along the same first direction in the second cell region 116to overlap the second MTJ 174 and the fourth MTJ 178.

Viewing from a top view perspective, each of the metal patterns from thefourth level metal patterns include rectangular shape extending alongthe Y-direction and overlapping the drain region and MTJ disposed ineach cell region. It should also be noted that each of the metalpatterns from the fourth level metal patterns is also coupled to ordirectly connected to a bit line (BL) for passing the signals.

Overall, in contrast to using the second level metal patterns to coupleto source line (SL) for transmitting signals in conventional MRAMdevice, the present invention preferably adjusts the layout of thediffusion region and first level metal patterns so that the first levelmetal patterns could be coupled to the source line SL directly. By usingthis design it would be desirable to save significantly more space inthe memory cell regions and also adjust the position of the MTJs toprevent misalignment between MTJs and metal interconnections underneath.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A layout pattern of a magnetoresistive randomaccess memory (MRAM), comprising: a substrate having a first cellregion, a second cell region, a third cell region, and a fourth cellregion; and a diffusion region on the substrate extending through thefirst cell region, the second cell region, the third cell region, andthe fourth cell region, wherein the diffusion region comprises a H-shapeand the H-shape comprises a portion overlapping the first cell region,the second cell region, the third cell region, and the fourth cellregion.
 2. The layout pattern of a MRAM of claim 1, wherein thediffusion region comprises: a first portion extending from the firstcell region to the third cell region along a first direction on thesubstrate; a second portion extending from the second cell region to thefourth cell region along the first direction on the substrate; a thirdportion extending from the first cell region to the second cell regionalong a second direction for connecting the first portion and the secondportion; a fourth portion extending from the third cell region to thefourth cell region along the second direction for connecting the firstportion and the second portion; and a fifth portion extending betweenthe third portion and the fourth portion along the second direction forconnecting the first portion and the second portion.
 3. The layoutpattern of a MRAM of claim 2, wherein the fifth portion overlaps thefirst cell region, the second cell region, the third cell region, andthe fourth cell region.
 4. The layout pattern of a MRAM of claim 2,further comprising: a first gate pattern extending from the first cellregion to the second cell region along the second direction; a secondgate pattern extending from the first cell region to the second cellregion along the second direction; a third gate pattern extending fromthe third cell region to the fourth cell region along the seconddirection; and a fourth gate pattern extending from the third cellregion to the fourth cell region along the second direction.
 5. Thelayout pattern of a MRAM of claim 4, further comprising: a first sourceregion on the third portion; a second source region on the fourthportion; and a third source region on the fifth portion.
 6. The layoutpattern of a MRAM of claim 5, further comprising: a first metal patternextending along the first direction overlapping and connecting the firstsource region, the second source region, and the third source region. 7.The layout pattern of a MRAM of claim 6, where the first metal patternis connected to a source line.
 8. The layout pattern of a MRAM of claim5, further comprising: a first drain region on the first cell regionbetween the first gate pattern and the second gate pattern; a seconddrain region on the second cell region between the first gate patternand the second gate pattern; a third drain region on the third cellregion between the third gate pattern and the fourth gate pattern; and afourth drain region on the fourth cell region between the third gatepattern and the fourth gate pattern.
 9. The layout pattern of a MRAM ofclaim 8, further comprising: a second metal pattern extending along thefirst direction overlapping and connecting the first drain region; athird metal pattern extending along the first direction overlapping andconnecting the second drain region; a fourth metal pattern extendingalong the first direction overlapping and connecting the third drainregion; and a fifth metal pattern extending along the first directionoverlapping and connecting the fourth drain region.
 10. The layoutpattern of a MRAM of claim 8, further comprising: a first magnetictunneling junction (MTJ) connecting the first drain region; a second MTJconnecting the second drain region; a third MTJ connecting the thirddrain region; and a fourth MTJ connecting the fourth drain region.